Supernumerary limbs in amphibians

Abstract

SYNOPSIS. Methods of generating supernumerary limbs by axial inversions of the regeneration blastema are described and recent data on this subject reviewed. The precise structure of supernumeraries has been determined by serially sectioning and examining muscle patterns. Supernumerary limbs from inversion of the antero-posterior or dorsoventral axis are always normal and of stump handedness. They regenerate well after amputation. Supernumeraries from inversion of both axes do not follow this pattern, but can be one of four classes of structure: normal, mirror symmetrical, partially mirror symmetrical or partially inverted. These four classes of supernumerary are described in detail. Their regenerative ability is also examined to reveal that precisely the same structure that was generated initially is regenerated. The implications of these findings for existing theories of pattern formation are discussed. © 1982 by the American Society of Zoologists.